Hydraulic energy recovery system with dual-powered auxiliary hydraulics

ABSTRACT

A power transfer system for a vehicle that comprises a an internal combustion engine, one or more drive wheels, and power transfer apparatus transfers power from the prime mover to the wheels for propelling the vehicle. The system further comprises an auxiliary hydraulic pump that has a drive shaft that coupled to a power take-off unit driven by engine, and to an auxiliary hydraulic motor powered by hydraulic fluid supplied from a hydraulic energy storage device such as an accumulator. As a result, the auxiliary hydraulic pump can be powered by hydraulic fluid from the accumulator when the prime mover is not operating, or by the prime mover when operating. A tandem arrangement of one way clutches can be employed to avoid the need to disconnect the auxiliary hydraulic pump from the prime mover during operation of the auxiliary hydraulic motor, and vice versa.

RELATED APPLICATIONS

This application is a continuation of U.S. Pat. No. 12/686,459, which isa continuation of U.S. patent application Ser. No. 11/692,698 filed Mar.28, 2007, which claims the benefit of U.S. Provisional Application No.60/786,793 filed Mar. 28, 2006, all of which are hereby incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

The invention herein described relates generally to a vehicle drivesystem that provides hydraulic energy storage and more particularly tosuch a system including auxiliary hydraulic circuits and components thatcan be powered by the vehicle's prime mover (e.g. engine) or bypressurized hydraulic fluid from the hydraulic energy storage. The powerdelivery system can be used on a variety of vehicle types, including inparticular garbage collection vehicles and other vehicles that makefrequent starts and stops and which have auxiliary hydraulic circuits.

BACKGROUND OF THE INVENTION

For many years there has been recognition that vehicles could be mademore fuel-efficient if the energy normally lost in decelerating orbraking the vehicle could be somehow collected, stored and reused toaccelerate the vehicle. A relatively large number of prior patents andpublished patent applications exist which are directed to variousaspects of this general approach. Some have proposed to collect andstore the energy in hydraulic accumulators and then reuse the energythrough fixed or variable displacement hydraulic transmissions. Therecovered energy was used to assist or provide vehicle motion.

Some vehicles, such as refuse trucks, had auxiliary hydraulic circuitsthat were powered by the vehicle's engine through a power take-off unit.Consequently, it was necessary for the engine to be running to operatethe auxiliary hydraulic systems on the truck. Typical auxiliaryhydraulic circuits included those use to actuate cylinders, powerhydraulic motors (other than those associated with vehicle propulsion),etc.

SUMMARY OF THE INVENTION

The present invention enables the use of stored hydraulic energy topower one or more auxiliary (other than vehicle propulsion) hydraulicsystems of a vehicle, thereby eliminating the need to keep an internalcombustion engine running. In a preferred embodiment, an auxiliaryhydraulic pump (also herein referred to as a body hydraulic pump) has adrive shaft that is coupled to a power take-off unit driven by a primemover, such as an internal combustion engine, and to an auxiliaryhydraulic motor powered by hydraulic fluid supplied from a hydraulicenergy storage device such as an accumulator. As a result, the auxiliaryhydraulic pump can be powered by hydraulic fluid from the accumulatorwhen the prime mover is not operating, or by the prime mover whenoperating. A tandem arrangement of one way clutches can be employed toavoid the need to disconnect the auxiliary hydraulic pump from the primemover during operation of the auxiliary hydraulic motor, and vice versa.In particular, a pair of sprag (one-way) clutches can be used such thatthe auxiliary hydraulic pump will be driven by the output shaft of thepower take off or hydraulic motor that is being driven faster.

More particularly, the invention provides a power transfer system for avehicle that comprises a prime mover, one or more drive wheels, and apower transfer apparatus that transfers power from the prime mover tothe wheels for propelling the vehicle. The power transfer apparatusincludes a power input shaft connected to the prime mover, a primaryhydraulic pump, a hydraulic drive motor, a pump coupling for couplingthe primary hydraulic pump to the power input shaft, a motor couplingfor coupling the hydraulic drive motor to an output drive shaft fordriving the one or more drive wheels, an energy storage device in whichenergy can be stored, primary hydraulic pump power circuitry forsupplying pressurized hydraulic fluid from the primary hydraulic pump tothe energy storage device, and hydraulic motor power circuitry fortransferring pressurized hydraulic fluid from the energy storage deviceto the hydraulic drive motor. The system also comprises an auxiliaryhydraulic pump for supplying hydraulic fluid to an auxiliary hydraulicsystem of the vehicle other than one that effects vehicle propulsion, apower take-off device driven by the power input shaft and drivinglyconnected to a drive shaft of the auxiliary hydraulic pump, and anauxiliary hydraulic motor powered by pressurized hydraulic fluid fromthe energy storage device and drivingly connected to the drive shaft ofthe auxiliary hydraulic pump for driving the drive shaft of theauxiliary hydraulic pump when not driven by the power take-off device.

The hydraulic drive motor may be reversely operable as a hydraulic pumpwhen driven by the output drive shaft for braking of the vehicle and toeffect energy recovery, and the hydraulic drive motor power circuitrymay be operable to transfer pressurized hydraulic fluid from thehydraulic drive motor/pump to the energy storage device when thehydraulic motor/pump is reversely driven during braking.

In a preferred embodiment, the power take-off device is coupled to theauxiliary hydraulic pump by a one way clutch, and the auxiliaryhydraulic motor is coupled to the auxiliary hydraulic pump by a one wayclutch, such that the auxiliary hydraulic pump will be driven by thepower take-off device or the auxiliary hydraulic motor that is beingdriven faster.

As will be appreciated by those skilled in the art, one or more of theprinciples of the present invention can be applied to any hydraulicdrive system employing one or more variable displacement drive motorswith or without the feature of hydraulic energy recovery.

Further features of the invention will become apparent from thefollowing detailed description when considered in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an exemplary vehicle drivesystem including a power drive unit according to the invention.

DETAILED DESCRIPTION

Referring now in detail to the drawings and initially to FIG. 1, anexemplary vehicle drive system according to the present invention isindicated generally by reference numeral 20. The vehicle drive system 20includes a power drive unit 21 connected between a prime mover 22 andthe drive wheel or wheels 23 of a vehicle generally denoted by referencenumeral 24. The prime mover preferably is an internal combustion (IC)engine, but other prime movers could also be used, such as gas turbines,electric motors and fuel cells. The power drive unit includes a powerinput shaft 26 to which the engine is drivingly connected by anysuitable means and an output drive shaft 27 drivingly connected to oneor more the wheels 23 of the vehicle by any suitable means, such as by adrive shaft 29 and transaxle 30.

The power drive unit 21 is characterized by a housing 33 that provides amount for one or more primary hydraulic pumps 34 and one or morehydraulic drive motors 35 (two being shown). The embodiment shown inFIG. 1 utilizes one reversible pump/motor unit 34 and two reversiblemotor/pump units 35 to drive the vehicle in a city or working mode. Thisarrangement optimizes the packaging of these units into the unitizedtransmission by using lower cost standard hydraulic units. It alsopermits more economical gearing from the dual power paths (lower toothloading), more responsive shift times (less mechanical inertia), asmaller overall package size and weight, and generally smootheroperation.

Each pump 34 and motor 35 may be a variable displacement type, and eachpreferably can be reversely driven to function as a motor or pump,respectively. By way of example, the pumps and motors may be axialpiston pumps and motors, wherein displacement of the pump/motor isvaried by changing the tilt angle of a tiltable swash plate, in a mannerthat is well known to those skilled in the art.

The housing contains a transmission assembly 37 to which the power inputshaft 26 and output drive shaft 27 are connected. The housing furtherprovides a mount for one or more auxiliary pumps 39 for cooling,lubrication, and/or low pressure systems along with a mounting positionfor a power take-off (PTO) device 40 that may be used to providehydraulic power to other parts of the vehicle. The auxiliary pumps maybe a stacked arrangement of pumps, particularly positive displacementpumps, driven by a common drive shaft. As depicted in FIG. 1, oneauxiliary pump may circulate hydraulic fluid through a cooler 42 andback to a reservoir 43. Another auxiliary pump may be used to supplypressurized fluid to the transmission assembly 37 and/or other drivecomponents for lubrication, and another auxiliary pump may be used tosupply low pressure fluid to components of the hereinafter describedhydraulic circuits to operate, for example, pilot valves used to controlfluid pressure components.

As illustrated in FIG. 1, the primary pump 34 is mounted to one axialend of the housing while the hydraulic motors 35 are mounted to theopposite axial end of the housing. In addition, the auxiliary pumps 39are mounted to the same axial side of the housing as the primary pump34. The motors and/or pumps may be otherwise mounted. For example, theprimary pump could be separately mounted, such as to the engine.

The vehicle drive system 20 further comprises an energy storage device46. In the illustrated embodiment the energy storage device is anaccumulator system including one or more pressurized fluid accumulators47, specifically hydropneumatic accumulators. Other energy storagedevices may be used such as a mechanical fly wheel or batteries. Theaccumulators 47 are supplied with pressurized fluid from the primarypump 34 and/or motors 35 by means of a high pressure manifold and fluidcircuitry generally indicated at 50. The fluid circuitry 50 is commandedby a system controller 52, more particularly an electronic systemcontroller, to control the flow of pressurized fluid to and from theaccumulators 47, the pump 34, motors 35 and other hydraulic components,including a flow restrictor 55, the function of which is discussedbelow. The system controller may include one or more microprocessors andassociated components programmed to carry out the herein describedoperations. The controller may have various inputs for receiving datafrom various sensors that monitor various operational parameters of thevehicle and various outputs by which the controller commands variousoperations.

In a first mode of operation, the position of the vehicle's acceleratorand brake pedals may be detected by sensors and act as input commands tothe electronic system controller 52. If the desired action is toaccelerate, say from a stop position, the electronic system controller52 can shift the transmission assembly 37 into a hydro low configurationto start the vehicle in motion. The controller may command the highpressure manifold and hydraulic circuitry 50 to supply high pressurefluid from the accumulator system 46 and/or the primary pump 34 (if thenoperating) to the hydraulic drive motors 35 to drive the output driveshaft 27 through the transmission assembly 58. This in turn will drivethe drive wheels 23 of the vehicle to accelerate the vehicle from thestopped position. The displacement of the drive motors may be varied bythe controller 52 to control the rate of acceleration to increase ormaintain a constant speed (zero acceleration). The drive motors canoperate to deliver high torque to the drive wheels of the vehicle.

If the vehicle is already moving and a desired action is to decelerateor brake the vehicle, the electronic system controller 52 directs thehigh pressure manifold and fluid circuitry 50 to receive high pressurefluid from the drive motors 35 which then will be reversely driven andact as pumps, thereby delivering high pressure fluid back to theaccumulator system 46. The hydraulic drive motors, acting as pumps, willgenerate resistance in the drive train to slow the vehicle down. Thisaction also recovers most of the kinetic energy from the vehicle andstores it in the accumulator system for future use by the drive systemor for performing other hydraulically powered work related tasks on thevehicle.

The vehicle may be provided with mechanical brakes that normally willnot be needed to decelerate the vehicle, but which will be available foruse if the braking force required (such as a panic stop) is greater thanthat which is being generated by the reversely driven hydraulic motorsacting as pumps, or as a back-up in case of a failure in the hydraulicdrive system.

Once the vehicle has accelerated to or past an upper end of the hydrolow range, such as about 25 mph, the electronic system controller 52commands the transmission assembly 37 to shift to a hydro high gearratio.

The transmission assembly 37 as thus far described corresponds to thetransmission assembly described in U.S. patent application Ser. No.11/379,883, which is hereby incorporated herein by reference. Referencemay be had to said patent application for further details of thetransmission assembly and its manner of operation for propelling andstopping a vehicle. Furthermore, a transmission assembly or moreparticularly a pump coupling may include a clutch 37A for selectivelydrivingly connecting the primary hydraulic pump 34 to the power inputshaft 26, and the transmission assembly may include a clutch 37B forselectively drivingly connecting the output drive shaft 27 to the powerinput shaft 26.

As above indicated, the power take-off (PTO) device 40 is used toprovide hydraulic power to other parts of the vehicle such as hydraulicactuators, motors, etc. that are typically operated when the vehicle isstationary or at least independently of the vehicle components involvedin the driving of the vehicle from one location to another. In the caseof a refuse truck, the power take-off can be used to supply power to thehydraulic cylinders used to compress the refuse in the refuse collectionchamber.

In accordance with the invention, one or more hydraulic body circuits 60may be provided for powering hydraulic components and systems other thanthose associated with propulsion of the vehicle and typically those thatare operated when the vehicle is stationary. Each hydraulic body circuit60 includes an auxiliary hydraulic pump 62 (also herein referred to as abody hydraulic pump) that has a drive shaft 63 coupled to the powertake-off device 40 that is driven by the engine 22, and to an auxiliaryhydraulic motor 65 powered by hydraulic fluid supplied from the energystorage device 46. As a result, the auxiliary hydraulic pump can bepowered by hydraulic fluid from the accumulators 47 when the engine isnot operating, or by the engine via the power take-off device when theengine is running.

In the illustrated preferred embodiment, the PTO device 40 is coupled bya sprag (one-way) clutch 68 to the auxiliary pump drive shaft 63. Theauxiliary hydraulic motor 65 likewise is coupled to the drive shaft ofthe pump by a sprag (one-way) clutch 70. If the PTO device and auxiliaryhydraulic motor are both being driven, the auxiliary hydraulic pump willbe driven by the PTO device or auxiliary hydraulic motor that is beingdriven faster. In most instances, however, only one of the PTO deviceand auxiliary hydraulic motor will be driven (under the control of thecontroller 52), in which case the other will be idle and the associatedone-way clutch will free-wheel.

While other arrangements are contemplated, in the illustrated embodimentthe PTO device 40 is drivingly connected to the input shaft 26 throughthe transmission assembly 37 which may include one or more clutches fordisengaging the PTO output shaft from the engine, such as when theengine is not running. As will be appreciated, though, the PTO devicecan remain drivingly connected to the engine even when the engine is notrunning.

Although the invention has been shown and described with respect to acertain preferred embodiment or embodiments, it is obvious thatequivalent alterations and modifications will occur to others skilled inthe art upon the reading and understanding of this specification and theannexed drawings. In particular regard to the various functionsperformed by the above described elements (components, assemblies,devices, compositions, etc.), the terms (including a reference to a“means”) used to describe such elements are intended to correspond,unless otherwise indicated, to any element which performs the specifiedfunction of the described element (i.e., that is functionallyequivalent), even though not structurally equivalent to the disclosedstructure which performs the function in the herein illustratedexemplary embodiment or embodiments of the invention. In addition, whilea particular feature of the invention may have been described above withrespect to only one or more of several illustrated embodiments, suchfeature may be combined with one or more other features of the otherembodiments, as may be desired and advantageous for any given orparticular application.

1-21. (canceled)
 22. A braking energy recovery system for use on avehicle having a powertrain with a driving portion that includes anengine, and with a driven portion that includes a transmission and adriveshaft connecting the transmission to a wheelset, the drivingportion of the powertrain being disengageably coupled to the drivenportion, the braking energy recovery system comprising: a first pump,being a variable displacement hydraulic pump, coupled to the drivenportion of the powertrain; a hydraulic accumulator connected to receivehydraulic fluid from the first pump, the accumulator being operative tostore hydraulic fluid under pressure; a hydraulic motor connected toreceive hydraulic fluid from the accumulator, the hydraulic motor beingisolated from the driven portion of the powertrain such that they canturn independently, the hydraulic motor also being coupled to thedriving portion of the powertrain; an auxiliary hydraulic system; and asecond hydraulic pump adapted to power the auxiliary hydraulic system,the second hydraulic pump being coupled to the hydraulic motor, suchthat it can be operated by the hydraulic motor.
 23. The braking energyrecovery system of claim 22, wherein the second hydraulic pump is alsocoupled to the driving portion of the powertrain, such that the secondhydraulic pump can also be operated by the driving portion of thepowertrain.
 24. The braking energy recovery system of claim 23, whereinthe hydraulic motor is adapted to operate the second pump through thedriving portion of the powertrain.
 25. The braking energy recoverysystem of claim 22 wherein the hydraulic motor is adapted to apply atorque to turn the engine, the torque assisting the engine toaccelerate, maintain a steady speed, turn idle, or power the auxiliarysystem.
 26. The braking energy recovery system of claim 24, wherein thehydraulic motor is adapted to apply a torque to turn the engine, thetorque assisting the engine to accelerate, maintain a steady speed, turnidle, or power the auxiliary system.
 27. The braking energy recoverysystem claim 22, further comprising a clutch selectively engaging thefirst pump with the driveshaft, and a gearbox between the driveshaft andthe first pump, the gearbox connecting the clutch to the first pump. 28.The braking energy recovery system of claim 22 further comprising acontroller operative to detect a braking demand and to modulate thedisplacement of the first pump according to the braking demand.
 29. Thebraking energy recovery system of claim 28, wherein the controller isfurther operative to modulate the displacement of the first pumpaccording to the storage availability of the accumulator.
 30. Thebraking energy recovery system of claim 28, wherein wherein thecontroller is further operative to detect an energy demand from theauxiliary hydraulic system and to modulate the displacement of thehydraulic motor according to the energy demand.
 31. The braking energyrecovery system of claim 28, wherein the hydraulic motor is coupled tothe driving portion of the powertrain, and the controller is operativeto adjust the displacement of the hydraulic motor to produce a torquecapable of turning the engine.
 32. The braking energy recovery system ofclaim 28, wherein the vehicle also has a base braking system, andwherein the controller is operative to activate and modulate the brakingforce of the base braking system according to the braking demand. 33.The braking energy recovery system of claim 22, wherein the maximumdisplacement of the first pump differs significantly from thedisplacement of the hydraulic motor.
 34. The braking energy recoverysystem of claim 32, wherein the system is retrofitted to an existingvehicle having a transmission with multiple fixed gear ratios.
 35. Thebraking energy recovery system of claim 26, wherein the system isretrofitted to an existing vehicle having a transmission with multiplefixed gear ratios.
 36. The braking energy recovery system of claim 22,wherein the auxiliary hydraulic system is a piece of hydraulicequipment.
 37. The braking energy recovery system of claim 36, whereinthe piece of hydraulic equipment is a garbage compactor of a refusetruck.
 38. The braking energy recovery system of claim 36, wherein thepiece of hydraulic equipment is a hydraulic lifting arm of a refusetruck adapted to lift a garbage can.